Incrementally-stretched adhesively-laminated films and methods for making the same

ABSTRACT

Incrementally-stretched adhesively-laminated films include two or more film layers adhesively bonded together. At least one of the two or more film layers is incrementally stretched. The incrementally-stretched adhesively-laminated films can have maintained or increased strength parameters despite a reduction in gauge. The incrementally-stretched adhesively-laminated films can be formed into bags for use as trash can liners or food storage. Methods of forming incrementally-stretched adhesively-laminated films include cold stretching one or more of the first and second film layers and adhesively bonding the film layers together.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.13/279,727 filed Oct. 24, 2011, which is a continuation in part of U.S.patent application Ser. No. 12/947,025 filed Nov. 16, 2010 and issued asU.S. Pat. No. 8,603,609 on Dec. 10, 2013, which claims the benefit ofU.S. Provisional Application No. 61/261,673, filed Nov. 16, 2009. Thecontents of the above applications are hereby incorporated by referencein their entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates generally to thermoplastic films.Specifically, the invention relates to stretched thermoplastic filmswith visually distinct regions created by stretching the films.

2. Background and Relevant Art

Thermoplastic films are a common component in various commercial andconsumer products. For example, grocery bags, trash bags, sacks, andpackaging materials are products that are commonly made fromthermoplastic films. Additionally, feminine hygiene products, babydiapers, adult incontinence products, and many other products includethermoplastic films to one extent or another.

The cost to produce products including thermoplastic film is directlyrelated to the cost of the thermoplastic film. Recently the cost ofthermoplastic materials has risen. In response, many attempt to controlmanufacturing costs by decreasing the amount of thermoplastic materialin a given product.

One way manufacturers may attempt to reduce production costs is tostretch the thermoplastic film, thereby increasing its surface area andreducing the amount of thermoplastic film needed to produce a product ofa given size. Common directions of stretching include “machinedirection” and “transverse direction” stretching. As used herein, theterm “machine direction” or “MD” refers to the direction along thelength of the film, or in other words, the direction of the film as thefilm is formed during extrusion and/or coating. As used herein, the term“transverse direction” or “TD” refers to the direction across the filmor perpendicular to the machine direction.

Common ways of stretching film in the machine direction include machinedirection orientation (“MDO”) and incremental stretching. MDO involvesstretching the film between pairs of smooth rollers. Commonly, MDOinvolves running a film through the nips of sequential pairs of smoothrollers. The first pair of rollers rotates at a speed less than that ofthe second pair of rollers. The difference in speed of rotation of thepairs of rollers can cause the film between the pairs of rollers tostretch. The ratio of the roller speeds will roughly determine theamount that the film is stretched. For example, if the first pair ofrollers is rotating at 100 feet per minute (“fpm”) and the second pairof rollers is rotating at 500 fpm, the rollers will stretch the film toroughly five times its original length. MDO stretches the filmcontinuously in the machine direction and is often used to create anoriented film.

Incremental stretching of thermoplastic film, on the other hand,typically involves running the film between grooved or toothed rollers.The grooves or teeth on the rollers intermesh and stretch the film asthe film passes between the rollers. Incremental stretching can stretcha film in many small increments that are evenly spaced across the film.The depth at which the intermeshing teeth engage can control the degreeof stretching. Often, incremental stretching of films is referred to asring rolling.

To MDO a film, manufacturers commonly heat the film to an elevatedtemperature and stretch the film in the machine direction. Commonly,manufacturers will stretch the thermoplastic film between approximately300 to 500 percent of the film's original length or more. Unfortunately,stretching thermoplastic films in the machine direction usingconventional methods can weaken the film.

Thermoplastic films have a variety of different strength parameters thatmanufacturers of products incorporating a thermoplastic film componentmay attempt to manipulate to ensure that the film is suitable for useits intended use. For example, the tensile strength of a thermoplasticfilm is the maximum stress that a film can withstand while beingstretched before it fails. The tear resistance of a thermoplastic filmis the amount of force required to propagate or enlarge a tear that hasalready been created in a film. Still further, impact resistance is theforce required to puncture a film.

Traditionally, thinner thermoplastic films can have undesirableproperties. For example, thinner thermoplastic films can have lowertensile strength, tear resistance, and impact resistance. In addition,thinner thermoplastic films can be more transparent or translucent.Consumers commonly associate thinner films with weakness. Such consumersmay feel that they are receiving less value for their money whenpurchasing products with thinner films; and thus, may be dissuaded topurchase thinner thermoplastic films.

Manufacturers may use laminates to achieve improved overall stiffnessand tear resistance. Although lamination of uniaxial layers can improvetear resistance transverse to the direction of stretching, tearing canbe easily effectuated along the longitudinal axis of stretching. Biaxialorientation of laminates can improve stiffness and tear resistance intwo directions, but the laminate can still be highly susceptible totears which run longitudinally along the combination of the axes.Further, conventional biaxial orientation methods used are not easilyadaptable to high speed production processes.

The weakening of a film upon stretching may dissuade manufacturers tostretch a film or use thinner films despite the potential materialsavings. For example, one common use of thermoplastic films is as bagsfor liners in trash or refuse receptacles. It is desirable to have trashbags with a high tear resistance to help prevent tearing of the trashbag and associated spilling of the contents during disposal thereof.Another common use of thermoplastic films is as flexible plastic bagsfor storing food items. Similar to trash bags, a high tear resistance infood storage bags can help prevent tearing of the bags and associatedspilling or spoiling of food.

Accordingly, there are a number of considerations to be made inthermoplastic films and manufacturing methods.

BRIEF SUMMARY OF THE INVENTION

Implementations of the present invention solve one or more problems inthe art with apparatus and methods for creating thermoplastic films withreduced gauge or thickness without unduly compromising the strengthparameters of the thermoplastic films. In particular, one or moreimplementations include adhesively-laminated incrementally-stretchedfilms with maintained or increased strength parameters. Suchimplementations can provide an overall thinner film employing a reducedamount of raw material that nonetheless has maintained or increasedstrength parameters.

For example, one implementation of an incrementally-stretchedadhesively-laminated film can include a first film layer and a secondfilm layer. The first film layer can have a first plurality ofun-stretched regions and a first plurality of stretched regionsintermittently dispersed about the first plurality of un-stretchedregions. The incrementally-stretched adhesively-laminated film canfurther include a plurality of adhesive bonds securing the first filmlayer to the second film layer.

Additionally, an implementation of a thermoplastic bag can include firstand second layers of thermoplastic material. The first layer can includefirst and second side walls joined along a bottom edge, a first sideedge, and an opposing second side edge. The second layer can includefirst and second side walls joined along a bottom edge, a first sideedge, and an opposing second side edge. One or more of the first layerand the second layer can be incrementally stretched. Also, the secondlayer can be positioned inside of the first layer. Furthermore, thesecond layer can be adhesively bonded to the first layer.

In addition to the foregoing, a method for forming anincrementally-stretched adhesively-laminated film can involve providinga first film layer comprising a thermoplastic material and providing atleast a second film layer. The method can also involve cold stretchingone or more of the first film layer and the second film layerincrementally. The method can additionally involve adhesively laminatingthe first film layer to the second film layer.

Additional features and advantages of exemplary embodiments of thepresent invention will be set forth in the description which follows,and in part will be obvious from the description, or may be learned bythe practice of such exemplary embodiments. The features and advantagesof such embodiments may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims. These and other features will become more fully apparent fromthe following description and appended claims, or may be learned by thepractice of such exemplary embodiments as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It should be noted that thefigures are not drawn to scale, and that elements of similar structureor function are generally represented by like reference numerals forillustrative purposes throughout the figures. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1A illustrates a schematic diagram of a thermoplastic film beingincrementally stretched by MD intermeshing rollers in accordance withone or more implementations of the present invention;

FIG. 1B illustrates an enlarged view of a portion of the thermoplasticfilm passing through the intermeshing rollers of FIG. 1A taken along thecircle 1B of FIG. 1;

FIG. 2 illustrates a view of an MD incrementally stretched film createdby passing through the intermeshing rollers of FIG. 1;

FIG. 3 illustrates a schematic diagram of a thermoplastic film beingincrementally stretched by TD intermeshing rollers in accordance withone or more implementations of the present invention;

FIG. 4 illustrates a view of a TD incrementally stretched film createdby passing through the intermeshing rollers of FIG. 3;

FIG. 5 illustrates a view of an MD and TD incrementally stretched filmcreated by the intermeshing rollers of both FIG. 1 and FIG. 3;

FIG. 6 illustrates a view of an incrementally stretched film created bypassing through diagonal direction intermeshing rollers in accordancewith one or more implementations of the present invention;

FIG. 7 illustrates a schematic diagram of a set of intermeshing rollersused to impart strainable networks into a film in accordance with one ormore implementations of the present invention;

FIG. 8 illustrates a view of an incrementally stretched film includingstrainable networks created by passing through the intermeshing rollersof FIG. 7;

FIG. 9 illustrates a view of another incrementally stretched filmincluding strainable networks in accordance with one or moreimplementations of the present invention;

FIG. 10 illustrates a cross-sectional view of an adhesively-laminatedincrementally-stretched film in accordance with one or moreimplementations of the present invention;

FIG. 11 illustrates a perspective view of another adhesively-laminatedincrementally-stretched in accordance with one or more implementationsof the present invention;

FIG. 12A illustrates a bag incorporating the adhesively-laminatedincrementally-stretched film of FIG. 10 in accordance with one or moreimplementations of the present invention;

FIG. 12B illustrates a cross-sectional view of the bag of FIG. 12A takenalong the line 12B-12B of FIG. 12A;

FIG. 13 illustrates another bag incorporating an adhesively-laminatedincrementally-stretched film in accordance with one or moreimplementations of the present invention;

FIG. 14 illustrates another bag incorporating an adhesively-laminatedincrementally-stretched film with an adhesive bond pattern in accordancewith one or more implementations of the present invention;

FIG. 15 illustrates another bag incorporating an adhesively-laminatedincrementally-stretched film that includes a top section with adhesivebonds in accordance with one or more implementations of the presentinvention;

FIG. 16 illustrates another bag incorporating an adhesively-laminatedincrementally-stretched film that includes top and bottom sections withadhesive bonds in accordance with one or more implementations of thepresent invention;

FIG. 17 illustrates another bag incorporating an adhesively-laminatedincrementally-stretched film having another bond pattern in accordancewith one or more implementations of the present invention;

FIG. 18 illustrates yet another bag incorporating anadhesively-laminated incrementally-stretched film having yet anotherpattern in accordance with one or more implementations of the presentinvention;

FIG. 19 illustrates still another bag incorporating anadhesively-laminated incrementally-stretched film having a middlesection without incremental stretching or bonds in accordance with oneor more implementations of the present invention;

FIG. 20 illustrates another bag incorporating an adhesively-laminatedincrementally-stretched film having only a top section with bonds inaccordance with one or more implementations of the present invention;

FIG. 21 illustrates another bag incorporating an adhesively-laminatedincrementally-stretched film having a top section and a bottom sectionwith different bond patterns in accordance with one or moreimplementations of the present invention;

FIG. 22 illustrates still another bag incorporating each of a differentpattern having a discontinuous bond pattern in accordance with one ormore implementations of the present invention;

FIG. 23 illustrates a schematic diagram of a bag manufacturing processin accordance with one or more implementations of the present invention;and

FIG. 24 illustrates a schematic diagram of another bag manufacturingprocess in accordance with one or more implementations of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One or more implementations of the present invention include apparatusand methods for creating thermoplastic films with reduced gauge orthickness without unduly compromising the strength parameters of thethermoplastic films. In particular, one or more implementations includeadhesively-laminated incrementally-stretched films with maintained orincreased strength parameters. Such implementations can provide anoverall thinner film employing a reduced amount of raw material thatnonetheless has maintained or increased strength parameters.

Indeed, one or more implementations can provide thermoplastic films, andproducts made therefrom, with reduced gauge yet maintained or increasedstrength parameters, such as tensile strength, tear resistance, andimpact resistance. Thus, one or more implementations can reduce thematerial needed to produce a product without compromising importantmaterial properties, such as tear resistance. One will appreciate inlight of the disclosure herein that such material reductions can providesignificant cost savings.

As alluded to previously, one or more implementations include filmshaving at least a first film layer that is incrementally stretched. Forexample, one or more implementations of the present invention includesincrementally stretching a film layer using MD ring rolling, TD ringrolling, diagonal direction (“DD”) ring rolling, embossing, or theformation of strainable networks, and combinations thereof.Incrementally stretching a film layer using the methods described hereincan impart ribs or other structures to the film and increase orotherwise modify one or more of the tensile strength, tear resistance,impact resistance, or elasticity of the film.

One or more implementations further include adhesively laminated filmlayers. At least one of the adhesively laminated film layers can beincremental stretched. As described more fully herein below, adhesivelamination can bond two or more film layers together without alteringthe ribs or other structures of the incrementally-stretched filmlayer(s).

As used herein, the terms “lamination,” “laminate,” and “laminatedfilm,” refer to the process, and resulting product, made by bondingtogether two or more layers of film or other materials. The term“bonding,” when used in reference to bonding of multiple layers of amulti-layer film, may be used interchangeably with “lamination” of thelayers. According to methods of one or more implementations of thepresent invention, adjacent layers of a multi-layer film are laminatedor bonded to one another. In one or more implementations, the laminationor bonding purposely results in a relatively weak bond between the filmlayers.

In particular, one or more implementations include methods ofincrementally stretching and adhesively bonding film layers with theunexpected result of maintaining or increasing the strength parametersof the resulting multi-layered film. In particular, as will be describedin greater detail below, one or more implementations provide synergisticeffects in the resultant multi-layered film. For example, one or moreimplementations include incrementally-stretched and adhesively-bondedfilms in which one or more of the strength parameters are unexpectedlygreater than the sum of the individual layers.

Implementations of the present invention include varying levels ofadhesion from light bonds that are easy to peal apart to very strongbonds. In one or more implementations, the bond strength can be lessthan the weakest tear strength of the individual layers so that thelamination bonds will break before the film will fail. In suchimplementations, the adhesive bonds between the layers can come apartunder stress and the individual layers can then react independently. Forexample, in the case of tensile strain, each film layer can reactindependently, leading to two peaks loads separated by elongation.

The unexpected or synergistic effects in one or more implementations canbe due at least in part to the fact that energy applied to theincrementally-stretched adhesively-laminated films in the form ofstresses and strains can first be absorbed through the breaking of theadhesive bonds between the film layers before causing materialdeformation (stretching, tearing, etc.) in the film layers. Furthermore,films of the present invention can undergo one or more film stretchingprocesses under ambient or cold (non-heated) conditions. This differssignificantly from most conventional processes that stretch films underheated conditions. Stretching under ambient or cold conditions inaccordance with one or more implementations can constrain the moleculesin the film so they are not as easily oriented as under heatedconditions. Such cold incremental stretching can help provide theunexpected result of maintaining or increasing the strength of athermoplastic film, despite a reduction in gauge.

In addition to the foregoing, one or more implementations providestretched thermoplastic films with physical features that consumers canassociate with the improved strength properties. In particular, one ormore implementations include thermoplastic films with ribs or otherstructures extending across the film in one or more directions. The ribscan serve to notify a consumer that the thermoplastic film has beenprocessed to increase the strength of the film.

Some consumers may associate thinner films with decreased strength.Indeed, such consumers may feel that they are receiving less value fortheir money when purchasing thermoplastic film products with smallergauges. One will appreciate in light of the disclosure herein that aconsumer may not readily detect that one or more incrementally-stretchedfilms of the present invention have a reduced gauge. In particular, byimparting an alternating pattern of thick and thin ribs, the consumermay associate the thickness of the thermoplastic film with that of thethicker ribs.

Film Materials

As an initial matter, the thermoplastic material of the films of one ormore implementations can include, but are not limited to, thermoplasticpolyolefins, including polyethylene and copolymers thereof, andpolypropylene and copolymers thereof. The olefin based polymers caninclude the most common ethylene or propylene based polymers such aspolyethylene, polypropylene, and copolymers such as ethylenevinylacetate (EVA), ethylene methyl acrylate (EMA) and ethylene acrylicacid (EAA), or blends of such polyolefins. Various other suitablepolyolefins will be apparent to one of skill in the art.

Other examples of polymers suitable for use as films in accordance withthe present invention include elastomeric polymers. Suitable elastomericpolymers may also be biodegradable or environmentally degradable.Suitable elastomeric polymers for the film includepoly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene),poly(ethylene-propylene), poly(styrene-butadiene-styrene),poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene),poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate),poly(ethylene-methylacrylate), poly(ethylene-acrylic acid),poly(ethylene butylacrylate), polyurethane,poly(ethylene-propylene-diene), ethylene-propylene rubber, andcombinations thereof. Additionally, the thermoplastic materials of oneor more films of the present invention can include a suitable amount ofa cling agent, such as polyisobutylene, to control the level oflamination during the lamination process.

In at least one implementation of the present invention, the film caninclude linear low density polyethylene. The term “linear low densitypolyethylene” (LLDPE) as used herein is defined to mean a copolymer ofethylene and a minor amount of an alkene containing 4 to 10 carbonatoms, having a density of from about 0.910 to about 0.926, and a meltindex (MI) of from about 0.5 to about 10. For example, someimplementations of the present invention can use an octene co-monomer,solution phase LLDPE (MI=1.1; p=0.920). Additionally, otherimplementations of the present invention can use a gas phase LLDPE,which is a hexene gas phase LLDPE formulated with slip/AB (MI=1.0;p=0.920).

One will appreciate that the present invention is not limited to LLDPE,and can include “low density polyethylene” (LDPE), and “very low densitypolyethylene” (VLDPE). The term “low density polyethylene” (LDPE) asused herein is defined to mean an ethylene-containing polymer having adensity of about 0.926 or lower and a MI of about 7. The term “very lowdensity polyethylene” (VLDPE) as used herein is defined to mean anethylene-based hexane copolymer having a density of from about 0.890 toabout 0.915 and a MI of from about 3 to about 17. Additionally, in oneor more implementations, the film can comprise high densitypolyethylene. The term “high density polyethylene” (HDPE) as used hereinis defined to mean an ethylene-containing polymer having a density of0.940 or higher. (Density (d) is expressed as g/cm 3). Indeed, filmsmade from any of the previously mentioned thermoplastic materials orcombinations thereof can be suitable for use with the present invention.

Indeed, implementations of the present invention can include anyflexible or pliable thermoplastic material which may be formed or drawninto a web or film. As described above, the film includes a plurality oflayers of thermoplastic films. Each individual film layer may include asingle layer or multiple layers. The thermoplastic material may beopaque, transparent, translucent, or tinted. Furthermore, thethermoplastic material may be gas permeable or impermeable.

As used herein, the term “flexible” refers to materials that are capableof being flexed or bent, especially repeatedly, such that they arepliant and yieldable in response to externally applied forces.Accordingly, “flexible” is substantially opposite in meaning to theterms inflexible, rigid, or unyielding. Materials and structures thatare flexible, therefore, may be altered in shape and structure toaccommodate external forces and to conform to the shape of objectsbrought into contact with them without losing their integrity. Inaccordance with further prior art materials, web materials are providedwhich exhibit an “elastic-like” behavior in the direction of appliedstrain without the use of added traditional elastic. As used herein, theterm “elastic-like” describes the behavior of web materials which whensubjected to an applied strain, the web materials extend in thedirection of applied strain, and when the applied strain is released theweb materials return, to a degree, to their pre-strained condition.

In addition to a thermoplastic material, films of one or moreimplementations of the present invention can also include one or moreadditives. For examples, the films can include pigments, slip agents,anti-block agents, tackifiers, voiding agents, or combinations thereof.The pigments can include TiO₂, or other pigments that can impart a colorand/or opacity to the film.

Indeed, implementations of the present invention can include anyflexible or pliable thermoplastic material which may be formed or drawninto a web or film. Furthermore, the thermoplastic materials may includea single layer or multiple layers. Examples of multilayered filmssuitable for use with one or more implementations of the presentinvention include coextruded multilayered films, multiple filmscontinuously laminated together, and multiple films partially ordiscontinuously laminated together. The thermoplastic material may beopaque, transparent, translucent, or tinted. Furthermore, thethermoplastic material may be gas permeable or impermeable.

One will appreciate in light of the disclosure herein that manufacturersmay form the individual films or webs to be discontinuously bondedtogether so as to provide improved strength characteristics using a widevariety of techniques. For example, a manufacturer can form a precursormix of the thermoplastic material and one or more additives. Themanufacturer can then form the film(s) from the precursor mix usingconventional flat or cast extrusion or coextrusion to produce monolayer,bilayer, or multilayered films.

It will be understood that where two or more layers are coextrudedtogether, the resulting film will be discontinuously bonded to anotherfilm at a later stage to provide the benefits associated with thepresent invention. Similarly, where a monolayer film is produced, themonolayer will later be discontinuously bonded to another film toprovide the increased strength characteristics associated with thepresent invention.

Alternative to conventional flat or cast extrusion processes, amanufacturer can form the films using other suitable processes, such as,a blown film process to produce monolayer, bilayer, or multilayeredfilms, which are similarly discontinuously bonded with another filmlayer at a later stage as will be described hereinafter. If desired fora given end use, the manufacturer can orient the films by trappedbubble, tenterframe, or other suitable processes. Additionally, themanufacturer can optionally anneal the films thereafter.

In one or more implementations, the films of the present invention areblown film or cast film. Blown film and cast film is formed byextrusion. The extruder used can be of a conventional design using adie, which will provide the desired gauge. Some useful extruders aredescribed in U.S. Pat. Nos. 4,814,135; 4,857,600; 5,076,988; 5,153,382;each of which are incorporated herein by reference in their entirety.Examples of various extruders, which can be used in producing the filmsto be used with the present invention, can be a single screw typemodified with a blown film die, an air ring, and continuous take offequipment. In one or more implementations, a manufacturer can usemultiple extruders to supply different melt streams, which a feed blockcan order into different channels of a multi-channel die. The multipleextruders can allow a manufacturer to form a multi-layered film withlayers having different compositions.

In a blown film process, the die can be an upright cylinder with acircular opening. Rollers can pull molten plastic upward away from thedie. An air-ring can cool the film as the film travels upwards. An airoutlet can force compressed air into the center of the extruded circularprofile, creating a bubble. The air can expand the extruded circularcross section by a multiple of the die diameter. This ratio is calledthe “blow-up ratio.” When using a blown film process, the manufacturercan collapse the film to double the plies of the film. Alternatively,the manufacturer can cut and fold the film, or cut and leave the filmunfolded.

As used herein, the term “starting gauge” or “initial gauge” refers tothe average distance between the major surfaces of a film before it isincrementally stretched so as to discontinuously bond adjacent layerstogether. Of course, it is also possible to stretch one or more of theindividual layers before they are discontinuously bonded together. Thefilms of one or more implementations of the present invention can have astarting gauge between about 0.1 mils to about 20 mils, suitably fromabout 0.2 mils to about 4 mils, suitably in the range of about 0.3 milsto about 2 mils, suitably from about 0.6 mils to about 1.25 mils,suitably from about 0.9 mils to about 1.1 mils, suitably from about 0.3mils to about 0.7 mils, and suitably from about 0.4 mils and about 0.6mils. Additionally, the starting gauge of films of one or moreimplementations of the present invention may not be uniform. Thus, thestarting gauge of films of one or more implementations of the presentinvention may vary along the length and/or width of the film.

As alluded to earlier, one or more implementations of the presentinvention include at least a first incrementally-stretched film layeradhesively laminated to at least a second film layer. The second filmlayer may be incrementally stretched, embossed, un-stretched, machinedirection oriented, or a combination thereof. Thus, one or more filmlayers of a multi-layered incrementally-stretched adhesively-laminatedthermoplastic film can include MD ring rolling, TD ring rolling, DD ringrolling, embossing, or the formation of strainable networks, andcombinations thereof. Each of the foregoing types of incrementalstretching is described below.

Referring now to the Figures, FIGS. 1A and 1B illustrate one exemplaryprocess of incrementally stretching a thermoplastic film. In particular,FIGS. 1A and 1B illustrate an MD ring rolling process that incrementallystretches a thermoplastic film 10 by passing the film 10 through a pairof MD intermeshing rollers 12, 14. The MD ring rolling processesstretches the film 10 in the machine direction.

As shown by FIGS. 1A and 1B, the first roller 12 and the second roller14 can each have a generally cylindrical shape. The rollers 12, 14 maybe made of cast and/or machined metal, such as, steel, aluminum, or anyother suitable material. The rollers 12, 14 can rotate in oppositedirections about parallel axes of rotation. For example, FIG. 1Aillustrates that the first roller 12 can rotate about a first axis 16 ofrotation in a counterclockwise direction 18. FIG. 1A also illustratesthat the second roller 14 can rotate about a second axis 20 of rotationin a clockwise direction 22. The axes of rotation 16, 20 can be parallelto the transverse direction and perpendicular to the machine direction.

The intermeshing rollers 12, 14 can closely resemble fine pitch spurgears. In particular, the rollers 12, 14 can include a plurality ofprotruding ridges 24, 26. The ridges 24, 26 can extend along the rollers12, 14 in a direction generally parallel to axes of rotation 16, 20.Furthermore, the ridges 24, 26 can extend generally radially outwardfrom the axes of rotation 16, 20. The tips of ridges 24, 26 can have avariety of different shapes and configurations. For example, the tips ofthe ridges 24, 26 can have a rounded shape as shown in FIG. 1B. Inalternative implementations, the tips of the ridges 24, 26 can havesharp angled corners. FIGS. 1A and 1B also illustrate that grooves 28,30 can separate adjacent ridges 24, 26. The configuration of the ridges24, 26 and grooves 28, 30 can dictate the amount stretching a filmpassing through the MD intermeshing rollers 12, 14 undergoes.

Referring specifically to FIG. 1B, various features of the ridges 24, 26and grooves 28, 30 are shown in greater detail. The pitch and depth ofengagement of the ridges 24, 26 can determine, at least in part, theamount of incremental stretching created by the intermeshing rollers 12,14. As shown by FIG. 1B, the pitch 32 is the distance between the tipsof two adjacent ridges on the same roller. The “depth of engagement”(DOE) 34 is the amount of overlap between ridges 24, 26 of the differentrollers 12, 14 during intermeshing. The ratio of DOE 34 to pitch 32 candetermine, at least in part, the amount of stretch imparted by a pair ofintermeshing rollers 12, 14.

As the thermoplastic film 10 passes between the intermeshing rollers 12,14, the ridges 24, 26 can incrementally stretch the film 10 in themachine direction. Additionally, the rollers 12, 14 can impart or form agenerally striped pattern 36 into the film 10. As used herein, the terms“impart” and “form” refer to the creation of a desired structure orgeometry in a film upon stretching the film that will at least partiallyretain the desired structure or geometry when the film is no longersubject to any strains or externally applied forces.

FIGS. 1A and 1B illustrate that the pre-stretched film 10 a comprises asingle-layered film. In one or more implementations, the individualfilms each comprises a plurality of laminated layers. Such layers may besignificantly more tightly bonded together than the adhesive bondingprovided top bond films together. Both tight and relatively weaklamination can be accomplished by joining layers by mechanical pressure,joining layers with adhesives, joining with heat and pressure, and evenspread coating and extrusion coating. Adjacent sub-layers of anindividual layer may be coextruded.

In any event, FIGS. 1A and 1B illustrate the intermeshing rollers 12, 14can process the pre-stretched film 10 a into an MDincrementally-stretched film 10 b. As previously mentioned, the MDincrementally-stretched film 10 b can include a striped pattern 36. Thestriped pattern 36 can include alternating series of“un-stretched”regions or thicker ribs 44 and stretched regions orthinner ribs 46. In one or more implementations, the “un-stretched”regions of the incrementally-stretched films may be stretched to a smalldegree. In any event, the “un-stretched” regions can be stretchedsignificantly less compared to the stretched regions.

The thicker ribs or un-stretched regions 44 can have a first averagethickness or gauge 48. The first average gauge 48 can be approximatelyequal to the starting gauge 42. In one or more implementations, thefirst average gauge 48 can be less than the starting gauge 42. Thethinner ribs or stretched regions 46 can have a second average thicknessor gauge 50. In one or more implementations, the second average gauge 50can be less than both the starting gauge 42 and the first average gauge48. In one or more implementations, the thicker ribs or un-stretchedregions 44 and the thinner ribs or stretched regions 46 are notcorrugated and lie in the same plane to give a ribbed flat film.

One will appreciate in light of the disclosure herein that the stripedpattern 36 may vary depending on the method used to incrementallystretch the film 10. To the extent that MD ring rolling is used toincrementally stretch the film 10, the striped pattern 36 on the film 10can depend on the pitch 32 of the ridges 24, 26, the DOE 34, and otherfactors.

FIG. 2 illustrates a top view of the MD incrementally-stretched film 10b. The ribs 44, 46 can extend across the film 10 b in a directiontransverse (i.e., transverse direction) to a direction in which the filmwas extruded (i.e., machine direction). The pitch 32 and the DOE 34 ofthe ridges 24, 26 of the MD intermeshing rollers 12, 14 can determinethe width and spacing of the ribs 44, 46. Thus, as explained in greaterdetail below, by varying the pitch 32 and/or DOE 34, the width and/orspacing of the ribs 44, 46, the amount of stretching the film undergoes,and the effects of the stretching on the physical properties can bevaried.

The ribs 44, 46 or ribbed pattern 36, can provide a pleasing appearanceand connote strength to a consumer. For example, the stripped pattern 36can signify that the MD incrementally-stretched film 10 b has undergonea physical transformation to modify one or more characteristics of theMD incrementally-stretched film 10 b. For example, MD ring rolling thefilm 10 can increase or otherwise modify one or more of the tensilestrength, tear resistance, impact resistance, or elasticity of the MDincrementally-stretched film 10 b. The ribbed pattern 36 can signify thephysical transformation to a consumer.

As mentioned previously, MD ring rolling is one exemplary method ofincrementally stretching a thermoplastic film to createvisually-distinct stretched regions in accordance with an implementationof the present invention. TD ring rolling is another suitable method ofincrementally stretching a film to create visually-distinct stretchedregions. For example, FIG. 3 illustrates a TD ring rolling process thatincrementally stretches a thermoplastic film 10 by passing the film 10through a pair of TD intermeshing rollers 52, 54. A TD ring rollingprocesses (and associated TD intermeshing rollers 52, 54) can be similarto the MD ring rolling process (and associated MD intermeshing rollers12, 14) described herein above, albeit that the ridges 56, 58 andgrooves 60, 62 of the TD intermeshing rollers 52, 54 can extendgenerally orthogonally to the axes of rotation 16, 20.

Thus, as shown by FIG. 3, as the thermoplastic film 10 passes betweenthe intermeshing rollers 52, 54, the ridges 56, 58 can incrementallystretch the film 10 in the transverse direction. In particular, as thefilm 10 proceeds between the intermeshing rollers 52, 54, the ridges 56,58 can impart or form a striped pattern 36 a into the film 10 to form aTD incrementally-stretched film 10 c.

FIG. 4 illustrates a view of the TD incrementally-stretched film 10 c.The striped pattern 36 a can include alternating series of thicker ribsor un-stretched regions 44 a and thinner ribs stretched regions 46 a. Inone or more implementations, the thicker ribs or un-stretched regions 44a and the thinner ribs or stretched regions 46 a are not corrugated andlie in the same plane to give a ribbed flat film. The incrementalstretching of the film 10 in the TD direction can modify one or more ofthe tensile strength, tear resistance, impact resistance, or elasticityof the TD incrementally-stretched film 10 c. The striped pattern 36 acan signify the transformation to a consumer.

Additionally, FIG. 4 illustrates that the stretched regions 46 a caninclude ribs that extend across the TD incrementally-stretched film 10 cin the machine direction. As shown by FIG. 4, the thinner ribs orstretched regions 46 a can extend across the entire width of the TDincrementally-stretched film 10 c. In alternative implementations,thinner ribs or stretched regions 46 a can extend across only a portionof the TD incrementally-stretched film 10 c. Similar to MD ring rolling,the pitch and the DOE of the ridges 56, 58 of the intermeshing rollers52, 54 can determine the width and spacing of the ribs or stretchedregions 46 a.

In still further implementations, a film 10 can undergo both an MD ringrolling process and a TD ring rolling process to create an MD and TDincrementally stretched film. For example, FIG. 5 illustrates a top viewof an MD and TD incrementally-stretched film 10 d. The MD and TDincrementally-stretched film 10 d can have a checker-board like pattern36 b. The checker-board like pattern 36 b can include alternating seriesof thicker ribs or un-stretched regions 44 b and thinner ribs orstretched regions 46 b, 46 c. The stretched regions 46 b, 46 c caninclude ribs 46 b that extend along the film 10 c in the machinedirection, and ribs 46 c that extend along the film in the transversedirection. As shown by FIG. 5, in one or more implementations, theaspect ratio of the rows and columns of the stretched regions 46 b, 46 ccan be approximately 1 to 1. In alternative implementations, the aspectratio of the rows and columns of the rows and columns of the stretchedregions 46 b, 46 c can be greater or less than 1 to 1, as explained ingreater detail in relation to FIG. 13. In one or more implementations,the thicker ribs or un-stretched regions 44 b and the thinner ribs orstretched regions 46 b, 46 c are not corrugated and lie in the sameplane to give a ribbed flat film.

The incrementally-stretched film regions created by MD and TD ringrolling can allow for even greater material savings by furtherincreasing the surface area of a given portion of film. Additionally, MDand TD ring rolling can provide properties or advantages not obtained byMD or TD ring rolling alone. Thus, checker-board like pattern 36 bcreated by the stretched regions 46 b, 46 c can signify thesetransformations to a consumer.

In yet further implementations, a manufacturer can use DD ring rollingto incrementally stretch a thermoplastic film to createvisually-distinct stretched regions. A DD ring rolling processes (andassociated DD intermeshing rollers) can be similar to the MD ringrolling process (and associated MD intermeshing rollers 12, 14)described herein above, albeit that the ridges and grooves of the DDintermeshing rollers can extend at an angle relative to the axes ofrotation. For example, FIG. 6 illustrates a view of a diagonallyincrementally-stretched film 10 e created by DD ring rolling. Thediagonally incrementally-stretched film 10 e can have a diamond pattern36 c. The diamond pattern 36 c can include alternating series ofdiamond-shaped ribs or un-stretched regions 44 c and stretched regions46 d. The stretched regions can include ribs 46 d oriented at an anglerelative to the transverse direction such that the ribs 46 d are neitherparallel to the transverse or machine direction. The illustratedconfiguration may be achieved with two ring rolling operations, similarto that of FIG. 5, but in which the DD ring rollers of each operationare angularly offset relative to one another (e.g., one providing anangle of about 45° off MD ring rolling, the other providing an angle ofabout 45° off TD ring rolling). In one or more implementations, thethicker ribs or un-stretched regions 44 c and the thinner ribs orstretched regions 46 d are not corrugated and lie in the same plane togive a ribbed flat film.

In accordance with another implementation, a structural elastic likefilm (SELF) process may be used to create a thermoplastic film withstrainable networks. As explained in greater detail below, thestrainable networks can include visually-distinct stretched regions.U.S. Pat. No. 5,518,801, U.S. Pat. No. 6,139,185; U.S. Pat. No.6,232,647; U.S. Pat. No. 6,394,651; U.S. Pat. No. 6,394,652; U.S. Pat.No. 6,513,975; U.S. Pat. No. 6,695,476; U.S. Patent ApplicationPublication No. 2004/0134923; and U.S. Patent Application PublicationNo. 2006/0093766 each disclose processes for forming strainable networksor patterns of strainable networks suitable for use with implementationsof the present invention. The contents of each of the aforementionedpatents and publications are incorporated in their entirety by referenceherein.

FIG. 7 illustrates a pair of SELF′ing intermeshing rollers 64, 66 forcreating strainable networks in a film. The first SELF′ing intermeshingroller 64 can include a plurality of ridges 68 and grooves 70 extendinggenerally radially outward in a direction orthogonal to an axis ofrotation 16. Thus, the first SELF′ing intermeshing roller 64 can besimilar to a TD intermeshing roller 52, 54. The second SELF′ingintermeshing roller 66 can include also include a plurality of ridges 72and grooves 74 extending generally radially outward in a directionorthogonal to an axis of rotation 20. As shown by FIG. 7; however, theridges 72 of the second SELF′ing intermeshing roller 66 can include aplurality of notches 76 that define a plurality of spaced teeth 78.

Referring now to FIG. 8, an incrementally-stretched film with strainablenetworks 10 f created using the SELF′ing intermeshing rollers 64, 66 isshown. In particular, as the film passes through the SELF′ingintermeshing rollers 64, 66, the teeth 78 can press a portion of the webout of plane to cause permanent, deformation of a portion of the film inthe Z-direction. On the other hand the portions of the film that passbetween the notched regions 76 and the teeth 78 will be substantiallyunformed in the Z-direction, resulting in a plurality of deformed,raised, rib-like elements 80. The length and width of rib-like elementscan depends on the length and width of teeth 78, and thus, can varybased on a desired pattern or desired result film property.

As shown by FIG. 8, the strainable network of theincrementally-stretched film 10 f can include first thicker ribs orun-stretched regions 44 d, second thicker ribs or un-stretched regions44 e, and thinner ribs or stretched transitional regions 46 e connectingthe first and second un-stretched regions 44 d, 44 e. The secondun-stretched regions 44 e and the stretched regions 46 e can form theraised rib-like elements 80 of the strainable network. The stretchedregions 46 e can be discontinuous or be separated as they extend acrossthe incrementally-stretched film with strainable networks 10 f in bothtransverse and machine directions. This is in contrast to ribs thatextend continuously across a film in one of the machine and transversedirections.

One will appreciate in light of the disclosure herein that the patternof the strainable network of FIG. 8 is only one pattern suitable for usewith the present invention. For example, FIG. 9 illustrates anotherstrainable network pattern that can include incrementally stretchedregions. In particular, FIG. 9 illustrates an incrementally-stretchedfilm 10 g with strainable networks. The strainable networks include aplurality of un-stretched regions 44 d that define a first region and aplurality of stretched regions 46 e that define a second region.Portions of the un-stretched regions 44 d, indicated generally as 45,extend in a first direction and are suitably substantially linear.Remaining portions of the un-stretched regions 44 d, indicated generallyas 47, extend in a second direction that is substantially perpendicularto the first direction, and the remaining portions 47 of theun-stretched regions 44 d are suitably substantially linear.

In one or more implementations, the first direction is perpendicular tothe second direction. Alternatively, other angular relationships existbetween the first direction and the second direction. Suitably, theangles between the first and second directions range from about 45° toabout 135°. In one or more implementations the angles between the firstand second direction is 90°. Intersecting sections of the portions 45and 47 of the un-stretched regions 44 d form boundaries 49 (only oneshown in FIG. 9), indicated by a phantom line in FIG. 9, whichcompletely surround the stretched areas 46 e. It should be understoodthat the boundaries 49 are not limited to the square shape illustratedherein and that boundaries 49 may comprise other shapes.

One or more implementations can include strainable network patternsother than those shown by FIGS. 8 and 9, or combinations of variouspatterns. Such patterns can include, but are not limited to,intermeshing circles, squares, diamonds, hexagons, or other polygons andshapes. Additionally, one or more implementations can include stretchedregions arranged in patterns that are combinations of the illustratedand described patterns/shapes. It should be understood that the term“pattern” is intended to include continuous or discontinuous sections ofpatterns, such as may result, for example, from the intersection offirst and second patterns with each other. Furthermore, the patterns canbe aligned in columns and rows aligned in the machine direction, thetransverse direction, or neither the machine or transverse directions.

In addition to ring rolling and SELFing, one or more implementations ofinclude using embossing, stamping, and other methods of incrementallystretching a film. In any event, one or more implementations includeincrementally stretching a film to thin and/or modify the strengthparameters of the film. As alluded to earlier, implementations canfurther include adhesively laminating an incrementally-stretched film toanother film (either un-stretched, incrementally stretched, MDO, orotherwise stretched).

For example, FIG. 10 illustrates a cross-sectional view ofincrementally-stretched adhesively-laminated film 10 h. Theincrementally-stretched adhesively-laminated film 10 h includes an MDincrementally-stretched film 10 b adhesively laminated to a TDincrementally-stretched film 10 c. In particular, FIG. 10 illustratesthat the MD incrementally-stretched film 10 b is adhesively laminated tothe TD incrementally-stretched film 10 c by bonds or bond areas 82. Thebond areas 82 can be separated in one or more implementations byun-bonded areas 84.

One will appreciate in light of the disclosure herein that altering thespacing and/or width of the bond areas 82 can affect the overallstrength of the incrementally-stretched adhesively-laminated film 10 h.For example, providing more bonded surface area relative to theun-bonded surface area can increase the density of such bonds that canabsorb forces, increasing the film strength. In particular, the breakingof the bonds 82 between the adjacent layers 10 b, 10 c can absorbforces, preventing such forces from contributing to failing of the film10 h. Such action can provide increased strength to the film. In one ormore implementations, the lamination bond includes a bond strength thatis advantageously less than the tear strength of each of the individualfilms so as to cause the lamination bond to fail prior to failing of thefilm layers.

In particular, strains applied to an incrementally-stretchedadhesively-laminated film of one or more implementations can cause thebonds 82 to fail (failure of the chemical bond created by the adhesive)before either of the individual layers undergo molecular-leveldeformation. For example, an applied strain can pull the bonds 82 apartprior to any molecular-level deformation (stretching, tearing,puncturing, etc.) of the films 10 b, 10 c. The chemical failure of thebonds can result in less resistive forces to an applied strain than thatexhibited by molecular-level deformation of the films.

One will appreciate in light of the disclosure herein that, inadditional implementations, the pre-laminated films 10 b, 10 c caninclude two or more joined layers. For example, the adhesively bondedlayers of an incrementally-stretched adhesively-laminated film cancomprise two or more coextruded layers or two or more continuouslylaminated layers. In addition to the possible compositional differencesbetween layers (e.g., 10 b, 10 c) of a given incrementally-stretchedadhesively-bonded film (e.g., 10 h), the different film layers can havediffering gauges or thicknesses.

The bond areas 82 shown in FIG. 10 bond the films 10 b, 10 c together atthe intersections of the thicker TD extending ribs 44 of MD stretchedfilm 10 b and the thicker MD extending ribs 44 a of TD stretched film 10c. The bond areas 82 are discontinuous in both the machine direction andthe transverse direction, and thus, form a discontinuous lamination.Discontinuous lamination refers to lamination of two or more layerswhere the lamination is not continuous in the machine direction and notcontinuous in the transverse direction. More particularly, discontinuouslamination refers to lamination of two or more layers with repeatingbonded patterns broken up by repeating un-bonded areas in both themachine direction and the transverse direction of the film.

In addition to discontinuous lamination, incrementally-stretchedadhesively-laminated films of one or more implementations can includepartially discontinuous lamination. Partially discontinuous laminationrefers to lamination of two or more layers where the lamination issubstantially continuous in the machine direction or in the transversedirection, but not continuous in the other of the machine direction orthe transverse direction. Alternately, partially discontinuouslamination refers to lamination of two or more layers where thelamination is substantially continuous in the width of the article butnot continuous in the height of the article, or substantially continuousin the height of the article but not continuous in the width of thearticle. More particularly, partially discontinuous lamination refers tolamination of two or more layers with repeating bonded patterns brokenup by repeating unbounded areas in either the machine direction or thetransverse direction.

For instance, an example of an incrementally-stretchedadhesively-laminated film including partially discontinuous lamentationis two MD incrementally-stretched films 10 b adhesively laminatedtogether along the thicker 44 TD extending ribs. Another example is twoTD incrementally-stretched films 10 c adhesively laminated along thethicker 44 a MD extending ribs.

One will appreciate in light of the disclosure herein that the bondareas of an incrementally-stretched adhesively-laminated film are notlimited to being located along the thicker ribs of an incrementallystretched film. For example, in one or more implementations the bondareas can secure the stretched areas (i.e., thinner ribs) of one film tostretched or un-stretched areas of another film. For example, adhesivebonds can connect the thicker ribs of one film to the thinner ribs ofthe other film.

FIG. 11 illustrates another incrementally-stretched adhesively-laminatedfilm 10 i. The incrementally-stretched adhesively-laminated film 10 iincludes first and second films 10 j, 10 k each comprisingmulti-directional strainable networks. The multi-directional strainablenetworks can provide stretch characteristics in multiple directions ofstrain, similar to that shown in FIG. 9.

A first region of the film 10 i can comprise un-bonded areas 86generally illustrated as bands of unformed material generally lying in aplane defined by the incrementally-stretched adhesively-laminated film10 i. A second region can comprise bond areas 88 that adhesively bondthe nub-like ribs 89 of the first and second films extending out of theplane. The ribs 89 can comprise a pattern extending in first and seconddistinct directions as formed by first and second superimposed patterns.

One will appreciate in light of the disclosure herein that theincrementally-stretched adhesively-laminated films can form part of anytype of product made from, or incorporating, thermoplastic films. Forinstance, grocery bags, trash bags, sacks, packaging materials, femininehygiene products, baby diapers, adult incontinence products, sanitarynapkins, bandages, food storage bags, food storage containers, thermalheat wraps, facial masks, wipes, hard surface cleaners, and many otherproducts can include incrementally-stretched adhesively-laminated filmsto one extent or another. Trash bags and food storage bags may beparticularly benefited by the films of the present invention.

Referring to FIGS. 12A and 12B, the incrementally-stretchedadhesively-laminated film 10 h illustrated in FIG. 10 is incorporated ina flexible draw tape bag 90. The bag 90 can include a bag body 92 formedfrom a piece of incrementally-stretched adhesively-laminated film 10 hfolded upon itself along a bag bottom 94. Side seams 96 and 98 can bondthe sides of the bag body 92 together to form a semi-enclosed containerhaving an opening 100 along an upper edge 102. The bag 90 alsooptionally includes closure means 104 located adjacent to the upper edge102 for sealing the top of the bag 90 to form a fully-enclosed containeror vessel. The bag 90 is suitable for containing and protecting a widevariety of materials and/or objects. The closure means 104 can compriseflaps, adhesive tapes, a tuck and fold closure, an interlocking closure,a slider closure, a zipper closure, a draw tape or other closurestructures known to those skilled in the art for closing a bag.

As shown, the sides of the bag body 92 can include un-stretched regions44 and stretched regions 46 in the form of ribs. The ribs can extendacross the bag 90 in the TD direction when the MDincrementally-stretched film 10 b is the outer layer. When the TDincrementally-stretched film 10 c is the outer layer, the ribs wouldextend across the bag 90 in the MD direction. As shown by FIGS. 12A and12B, discontinuous bond areas 82 adhesively bond the outer MDincrementally-stretched film 10 b to the inner TDincrementally-stretched film 10 c.

The bag 90 can require less material to form than an identical bagformed with an un-stretched film 10 a of the same thermoplasticmaterial. Additionally, despite requiring less material, the bag 90 caninclude improved properties imparted by incremental stretching and theadhesive bonding. The striped pattern 36 and/or the bond areas 82 canserve to notify a consumer of the improved properties.

Furthermore, as shown by FIGS. 12A and 12B, a bag 90 formed from anincrementally-stretched adhesively-laminated film can have a first layerof thermoplastic material (i.e., film 10 b). The first layer (i.e., film10 b) can include first and second side walls joined along a bottomedge, a first side edge, and an opposing second side edge; thereby,forming a first bag. In particular, the bottom edge of the first layer(i.e., film 10 b) can comprise a fold. The bag 90 can also include asecond layer of thermoplastic material (i.e., film 10 c). The secondlayer (i.e., film 10 c) can include including first and second sidewalls joined along a bottom edge, a first side edge, and an opposingsecond side edge; thereby, forming a second bag.

As shown by FIG. 12B, the second layer (i.e., film 10 c) is positionedwithin the first layer (i.e., film 10 b). Furthermore, in theimplementation shown in FIGS. 12A and 12B, both the first layer (i.e.,film 10 b) and the second layer (i.e., film 10 c) are incrementallystretched. In any event, the first layer (i.e., thermoplastic film 10 b)and the second layer (i.e., thermoplastic film 10 c) are adhesivelybonded to each other. Thus, a first side wall 103 of the bag 90 cancomprise a first layer (i.e., film 10 b) non-continuously and adhesivelylaminated to the second layer (i.e., film 10 c). Similarly, a secondside wall 105 of the bag 90 can also comprise a first layer (i.e., film10 b) non-continuously and adhesively laminated to the second layer(i.e., film 10 c).

FIG. 13 illustrates a tie bag 106 incorporating anincrementally-stretched adhesively-laminated film including two MD andTD incrementally-stretched and adhesively-bonded films similar to film10 d of FIG. 5. The tie bag 106 includes a pattern of un-stretchedregions 44 f and stretched regions 46 f, 46 g created by MD and TD ringrolling. As shown by FIG. 13, bond areas 82 a on the un-stretchedregions 44 f can adhesively bond the inner and outer layers of each sidewall of the bag 106. The stretched regions can include ribs 46 f thatextend across the bag 106 in the machine direction. Additionally, thestretched regions can include ribs 46 g that extend across the bag 106in the transverse direction, or in other words from the bag bottom 108to flaps 110 of an upper edge 112 of the bag 106.

In comparison with the film 10 d of FIG. 5, the spacing between the MDextending ribs 46 f and the TD extending ribs 46 g is greater in the bag106. Ring rolls having a greater pitch can create this difference inspacing. Furthermore, the relative spacing between the MD extending ribs46 f and the TD extending ribs 46 g differs in the bag 106, whilerelative spacing is the same in the film 10 d. Using TD ring rollshaving a greater pitch than the pitch of the MD ring rolls can createthis effect.

FIGS. 14-22 illustrate additional implementations of multi-layer bags114 a-i that include incrementally-stretched adhesively-laminated films.In one or more implementations, such as FIGS. 14-16, each bonded pattern15, 16 can have a largest TD patterned width 118 in the transversedirection (TD) of less than about 25% of the transverse width 119 of thepatterned film, or less than about 20% of the transverse width 113 ofthe film, or less than about 10% of the transverse width 119 of thepatterned film, or less than about 5% of the transverse width 113 of thefilm. In one or more implementations, the bonded patterns have a largestMD patterned width 120 in the machine direction of less than about 25%of the machine width 121 of the patterned film, or less than about 20%of the machine width 111 of the film, or less than about 10% of themachine width 111 of the film, or less than about 5% of the transversewidth 111 of the film.

As shown by FIG. 14, in one or more implementations the width 118 of thebonded patterns in the transverse direction may be greater than thewidth of the un-bonded areas 122 in the transverse direction. Similarly,the width 120 of the bonded patterns in the machine direction may begreater than the width of the un-bonded areas 123 in the machinedirection.

The bonded areas can also be large in comparison to un-bonded areas, forexample as seen in FIGS. 14-16. For example, bonded areas ofdiscontinuous lamination can represent at least about 50% of the totalarea of the section where the discontinuous lamination occurs, or atleast about 60% of the total area of the section where the discontinuouslamination occurs, at least about 70% of the total area of the sectionwhere the discontinuous lamination occurs, at least about 80% of thetotal area of the section where the discontinuous lamination occurs.

In other implementations, for example in FIGS. 17-18, the bonded areasof discontinuous lamination can represent substantially less than about50% of the total area of the section where the discontinuous laminationoccurs, or less than about 40% of the total area of the section wherethe discontinuous lamination occurs, or less than about 30% of the totalarea of the section where the discontinuous lamination occurs, or lessthan about 10% of the total area of the section where the discontinuouslamination occurs.

Additionally, a manufacturer can vary the size of the bond areas. Forexample, the bag 114 a of FIG. 14 includes relatively large square bondareas 115, while the bag 114 b of FIG. 15 includes smaller square bondareas 115 a. Similarly, a manufacturer can vary the shape of the bondareas as shown by the square 115, 115 a, diamond 116, and circular 117bond areas of bags 114 a-114 d of FIGS. 14-17.

In addition to varying the pattern of bond areas in a bag or film, oneor more implementations include providing bond areas in certain sectionsof a bag or film, and only un-bonded regions in other sections of thebag or film. For example, FIG. 15 illustrates a multi-layered bag 114 bhaving an upper section 124 including a plurality of bonded areas 115 a,and a lower section 125 devoid of bonded areas. In alternativeimplementations, the upper section 124 can have no bonded areas, and thelower section can include a plurality of bonded areas 115 a. FIG. 16, onthe other hand illustrates a multi-layered bag 114 c having upper andlower sections 124, 125 including a plurality of bonded areas 116, and amiddle section 126 devoid of bonded areas. In alternativeimplementations, the middle section may include a plurality of bondedareas 116, and the upper and lower sections 124, 125 can have no bondedareas. In any case, certain sections of a film or bag may be void ofbonded areas, while others include bonded areas.

Furthermore, one or more implementations include providing differentbond patterns in different sections of a bag or film. For example, FIG.21 illustrates a bag 114 h having square bonds 115 a in an upper section124, and linear bonds 127 in a lower section 125. In addition todifferent bond patterns, a manufacturer can vary the continuity of thebond patterns. Along these lines, FIGS. 19, 20, and 21 illustratemulti-layered bags with partially discontinuous linear bond areas 127,while FIG. 22 illustrates discontinuous linear bond areas 128.

Still further the bond areas can correspond to the type of incrementalstretching or can be independent therefrom. For example, bags 114 f-114i include linear bond areas 127, 128 corresponding to ribs created by TDring rolling. In alternative implementations, can be independent of theincremental stretching of one or more of the layers of the bag. Forexample, when an un-stretched or continuously stretched film is theouter layer of the bag, the bond areas may not correspond to theincremental stretching of the inner layer. Still further, the pattern,location, and shape of the adhesive applied to one or more of the layersof the multi-layer bag 90, 106, 114 a-114 i can dictate the bond areas.

One will appreciate in light of the disclosure herein that amanufacturer can tailor specific sections, zones, and/or layers of a bagor film with desirable properties by varying the amount, location,types, and/or number of forms of incremental stretching. For example, amanufacturer can provide one or more sections (upper, lower, middle) orlayers (inner, outer, middle) of a bag with one set of propertiescreated by one or more forms of incremental stretching, and provideanother section or layer with another set of properties created byanother (or combination) of incremental stretching. Thus, one willappreciate in light of the disclosure herein that a manufacturer cantailor specific sections or zones of a bag or film with desirableproperties by MD, TD, or DD ring rolling, SELF′ing, or combinationsthereof. Furthermore, the different ribs and/or bonded area can serve tonotify a consumer of the properties of the different sections.

Implementations of the present invention can also include methods offorming incrementally-stretched adhesively-laminated film and bagsincluding the same. FIGS. 23-25 and the accompanying descriptiondescribe such methods. Of course, as a preliminary matter, one ofordinary skill in the art will recognize that the methods explained indetail herein can be modified. For example, various acts of the methoddescribed can be omitted or expanded, additional acts can be included,and the order of the various acts of the method described can be alteredas desired.

FIG. 23 illustrates an exemplary embodiment of a high-speedmanufacturing process 200 for producing incrementally-stretchedadhesively-laminated films and bags therefrom. According to the process200, a first thermoplastic film layer 10 and a second thermoplastic filmlayer 10 a are unwound from rolls 201, 202 and directed along a machinedirection.

The process 200 can then include incrementally stretching one or more ofthe first film layer 10 and the second film layer 10 a. For example, thefirst film layer 10 can pass between first and second cylindricalintermeshing rollers 204, 206 to incrementally stretch the film 10. Theintermeshing rollers 204, 206 can have a construction similar to that ofintermeshing rollers 12, 14 of FIGS. 1A-1B, or any of the otherintermeshing rollers shown or described herein. The rollers 204, 206 maybe arranged so that their longitudinal axes are perpendicular to themachine direction. Additionally, the rollers 204, 206 may rotate abouttheir longitudinal axes in opposite rotational directions. In variousembodiments, motors may be provided that power rotation of the rollers204, 206 in a controlled manner. As the film layer 10 passes between thefirst and second rollers 204, 206, the ridges and/or teeth of theintermeshing rollers 204, 206 can form an incrementally-stretched film207.

Additionally, the second film layer 10 a can optionally pass betweenthird and fourth intermeshing rollers 208, 210 to incrementally stretchthe film 10 a. The intermeshing rollers 208, 210 can have a constructionsimilar to that of intermeshing rollers 204, 206, or any of the otherintermeshing rollers shown or described herein. As the film layer 10 apasses between the third and fourth intermeshing rollers 208, 210, theridges and/or teeth of the intermeshing rollers 204, 206 can form anincrementally-stretched film 209. In alternative implementations, theprocess 200 may omit incrementally stretching the second film layer 10a. Still further, the process can optionally include continuouslystretching the second film layer 10 a, embossing the second film layer10 a, or otherwise processing the second film layer 10 a.

Incrementally stretching one or more of the films 10, 10 a can modifyand/or increase one or more of the physical properties of one or more ofthe films 10, 10 a and/or increase the surface area of one or more ofthe films 10, 10 a and/or reduce the gauge of one or more of the films10, 10 a. Furthermore, incrementally stretching one or more of the films10, 10 a can provide one or more of the films 10, 10 a with a visualpattern that can serve to notify a consumer that one or more of thefilms 10, 10 a has been processed to enhance one or more properties.

One will appreciate that when both the first film layer 10 and thesecond film layer 10 a are incrementally stretched, they can undergo thesame type and/or degree of stretching or different types and/or degreesof stretching. For example, in one or more implementations, the firstand second intermeshing rollers 204, 206 and the third and fourthintermeshing rollers 208, 210 can both comprise MD ring rollers 12, 14,but with different pitches and/or DOEs. Still further, first and secondcylindrical intermeshing rollers 204, 206 can comprise MD ring rollers12, 14, while the third and fourth intermeshing rollers 208, 210comprise MD ring rollers 52, 54. Still further first and secondcylindrical intermeshing rollers 204, 206 can comprise ring rollers,while third and fourth intermeshing rollers 208, 210 comprise SELFingrollers 64, 66.

Additionally, while not shown in FIG. 23, one or both the first filmlayer 10 and the second film layer 10 a can undergo a second incrementalstretching process after respectively passing through the intermeshingrollers 204, 206, 208, 210. For example, one or more of the first filmlayer 10 and the second film layer 10 a can pass through a second,sequential set of intermeshing rollers. For example, the first filmlayer 10 can pass through a first set of MD ring rollers (i.e., 204,206) and then through a second sequential set of TD intermeshing rollerssuch that the incrementally-stretched film 207 is both MD and TD ringrolled. Thus, one or more of the first film layer 10 and the secondlayer 10 a can undergo any number or combination of the incrementalstretching processes described herein above.

During the manufacturing process 200, the incrementally stretched film10, 10 a can also pass through pairs of pinch rollers 212, 214, 216,218. The pinch rollers 212, 214, 216, 218 can be appropriately arrangedto grasp the films 10, 10 a. The pinch rollers 212, 214, 216, 218 mayfacilitate and accommodate the films 10, 10 a.

The process 200 can also involve applying an adhesive to one or more ofthe films 10, 10 a. For example, FIG. 23 illustrates that an applicator220 can apply an adhesive to one or more of the lower surface of thefilm 10 or the upper surface of the film 10 a. The adhesive can comprisehot melt adhesive, a cold glue, an olefinic adhesive to facilitatereclaiming, a pressure sensitive adhesive, or other suitable adhesives.The manufacturer can use the applicator 220 to control the amount ofadhesive (i.e., coat weight). In one or more implementations, themanufacturer can control the coat weight of the adhesive to ensure alight bond such that upon applying a strain to the finishedincrementally-stretched adhesively-laminated film the first and secondfilm layers will delaminate prior to either the first or second filmlayers failing.

The applicator 220 can control the pattern of adhesive applied to one ormore of the films 10, 10 a, and thus, the pattern of the bond areas. Inparticular, the applicator 220 can apply adhesive to one or more of thefilms 10, 10 a in a pattern such as those described herein above inrelation to FIGS. 14-22 (stripes, checkerboard, circles, squares,diamonds, etc.). In alternative implementations, the applicator 220 canapply adhesive to one or more of the films 10, 10 a in a spider web likepattern, omega patterns, dots, stitching patterns, widely spacedpatterns, or other patterns. Still further, the applicator 220 can applyadhesive in a continuous pattern, discontinuous pattern, or partiallydiscontinuous pattern. Furthermore, the applicator 220 can control whereon the films 10, 10 a adhesive is applied. Thus, the applicator 220 canapply adhesive to one or more regions or zones of the films 10, 10 a.

Additionally, one or more implementations can include filamentation orfiberization of the adhesive. For example, the applicator 220 canproduce filament strands of adhesive. The applicator 220 can then useheated air to elongate the strands of adhesive and apply them to one ormore of the films 10, 10 a in random or ordered patterns. Suchfiberization of the adhesive can allow for the control of the coatweight and reduce the amount of adhesive required for a desired bondstrength.

After an adhesive is applied to one or more of the films 10, 10 a, thefilms 10, 10 a can pass together through a pair of nip or pinch rollers222, 224. The nip rollers 222, 224 can press the films 10, 10 a togetherthereby allowing the adhesive to bond the films 10, 10 a together toform an incrementally-stretched adhesively-laminated film 226. Inparticular, pistons attached to the nip rollers 222, 224 can actuate thenip rollers 222, 224 to apply a force or pressure to the films 10, 10 a.

To produce a finished bag, the processing equipment may further processthe incrementally-stretched adhesively-laminated film 226 after thelamination operation. For example, a folding operation 228 can fold theincrementally-stretched adhesively-laminated film 226. The foldingoperation 228 can fold the incrementally-stretched adhesively-laminatedfilm 226 with visually-distinct stretched regions in half along thetransverse direction. In particular, the folding operation 228 can movea first edge 230 adjacent to the second edge 232, thereby creating afolded edge 234. The folding operation 228 thereby provides a first filmhalf 236 and an adjacent second web half 238. The overall width 240 ofthe second film half 238 can be half the width 242 of the pre-foldedincrementally-stretched adhesively-laminated film 226.

Optionally, a draw tape operation 260 can insert a draw tape 262 intothe incrementally-stretched adhesively-laminated film 226. Furthermore,a sealing operation 264 can form the parallel side edges of the finishedbag by forming heat seals 266 between adjacent portions of the foldedincrementally-stretched adhesively-laminated film 226. The heat seals266 may be spaced apart along the folded incrementally-stretchedadhesively-laminated film 226 with visually-distinct stretched regions.The sealing operation 264 can form the heat seals 266 using a heatingdevice, such as, a heated knife.

A perforating operation 268 may form a perforation 270 in the heat seals266 using a perforating device, such as, a perforating knife. Theperforations 270 in conjunction with the folded outer edge 234 candefine individual bags 272 that may be separated from theincrementally-stretched adhesively-laminated film 226. A roll 274 canwind the incrementally-stretched adhesively-laminated film 226 embodyingthe finished bags 272 for packaging and distribution. For example, theroll 274 may be placed into a box or bag for sale to a customer.

In still further implementations, the folded incrementally-stretchedadhesively-laminated film 226 may be cut into individual bags along theheat seals 266 by a cutting operation. In another implementation, thefolded incrementally-stretched adhesively-laminated film 226 may befolded one or more times prior to the cutting operation. In yet anotherimplementation, the side sealing operation 264 may be combined with thecutting and/or perforation operations 268.

One will appreciate in light of the disclosure herein that the process200 described in relation to FIG. 23 can be modified to omit or expandedacts, or vary the order of the various acts as desired. For example,three or more separate film layers can be incrementally stretched andlaminated together to form an incrementally-stretchedadhesively-laminated film 226.

FIG. 24 illustrates yet another manufacturing process 278 for producingan incrementally-stretched adhesively-laminated film and bags therefrom.The process 278 can be similar to process 200 of FIG. 23, except thatthe films 10, 10 a are folded in half to form c-folded films prior towinding on the rolls 201 a, 202 a. Thus, in such implementations, thefilms 10, 10 a unwound from the rolls 201 a, 202 a are already folded.

Additionally, the manufacturing process 278 illustrates that afterpassing through intermeshing rollers 204, 206, the film 10 can passthrough another set of intermeshing rollers 280, 282 to incrementallystretch the film 10 a second time. The intermeshing rollers 280, 282 canhave a construction similar to that of intermeshing rollers 52, 54 ofFIG. 3, or any of the other intermeshing rollers shown or describedherein.

Additionally, FIG. 24 illustrates that an insertion operation 294 caninserting the folded film 10 into the folded film 10 a. Insertionoperation 294 can combine and adhesively laminate the folded films 10,10 a using any of the apparatus and methods described herein in U.S.patent application Ser. No. 13/225,930 filed Sep. 6, 2011 and entitledApparatus For Inserting A First Folded Film Within A Second Folded Filmand Ser. No. 13/225,757 filed Sep. 6, 2011 and entitled Method ForInserting A First Folded Film Within A Second Folded Film, each of whichare incorporated herein by reference in their entirety.

As alluded to earlier, incrementally-stretched adhesively-laminatedfilms of one or more implementations can provide an overall thinner filmemploying a reduced amount of raw material that nonetheless hasmaintained or increased strength parameters. The following examplespresent the results of a series of tests performed on thermoplasticfilms that have been incrementally stretched and then adhesivelylaminated in accordance with one or more implementations of the presentinvention. These examples are illustrative of the invention claimedherein and should not be construed to limit in any way the scope of theinvention.

Example 1

In a first example, a first layer of a base film having a core ply ofLLDPE with white pigment and outer plies of LLDPE\LDPE\Antiblock blendwas cold MD ring rolled to form an MD ring rolled (RR) film. The MDintermeshing rolls used in Example 1 had a 0.100″ pitch and were set ata DOE of 0.110″. A second layer of the base film was cold TD ring rolledto form a TD RR film. The TD intermeshing rolls used in Example 1 had a0.060″ pitch and were set at a DOE of 0.032″. The MD RR film and the TDRR film were then laminated together using a butene-1-copolymer, hotmelt adhesive, Rextac® RT 2730 at four different coat weights shown inTables I, II, and III as samples 1-4. Tables I, II, and III also showscomparative properties of the base film, the MD RR film, the TD RR film,the combined MD RR and TD RR films not adhesively laminated together, aswell as a thicker film.

TABLE I Dynatup and Tear Resistance of Incrementally-StretchedAdhesively- Laminated Films (1 layer MD RR and 1 layer TD RR) DynatupDynatup Energy Coat Gage Tensile Peak to max MD Weight by Wt. Peel Loadload (in. Tear TD Tear g/sq. ft. (mils) (g-f) (lb-f) lb-f) (g) (g)Sample 1 0.225 0.84 N/A 11.3 8.4 434 585 Sample 2 0.056 0.84 N/A 11.111.2 496 539 Sample 3 0.015 0.84 61 10.5 9.2 387 595 Sample 4 0.012 0.8457 11.3 10.4 425 643 Comparison Data Un-laminated NA 0.84 N/A 9.4 6.9326 502 Combined MD and TD RR Films TD RR Film NA 0.4 N/A 4.6 4.4 101 60MD RR Film NA 0.44 N/A 5.4 4.8 173 475 Base Film NA 0.6 N/A 5.1 6.3 298473 Thicker Base NA 0.9 NA 4.3 3.8 262 843 Film

TABLE II MD Tensile Properties of Incrementally-Stretched Adhesively-Laminated Films (1 layer MD RR and 1 layer TD RR) MD MD MD MD MD TensileTensile Tensile Tensile Tensile Yeild Peak 1 Strain 1 Peak 2 Strain 2(lb-f) (lb-f) (%) (lb-f) (%) Sample 1 0.33 4.5 N/A 11.3 8.4 Sample 20.43 4.9 N/A 11.1 11.2 Sample 3 0.55 4.0 61 10.5 9.2 Sample 4 0.5 3.8 5711.3 10.4 Comparison Data Un-laminated 0.64 4.2 N/A 9.4 6.9 Combined MDand TD RR Films TD RR Film 0.27 1.7 N/A 4.6 4.4 MD RR Film 0.29 2.6 N/A5.4 4.8 Base Film 0.73 4.1 N/A 5.1 6.3 Thicker Base 1.42 7.2 NA 4.3 3.8Film

TABLE III TD Tensile Properties of Incrementally-Stretched Adhesively-Laminated Films (1 layer MD RR and 1 layer TD RR) TD TD TD TD TD TensileTensile Tensile Tensile Tensile Yeild Peak 1 Strain 1 Peak 2 Strain 2(lb-f) (lb-f) (%) (lb-f) (%) Sample 1 1.58 2.0 341 N/A N/A Sample 2 1.532.0 557 1.80 750 Sample 3 1.4 2.1 489 1.90 825 Sample 4 1.3 1.9 558 1.80800 Comparison Data Un-laminated 1.3 2.1 368 1.50 650 Combined MD and TDRR Films TD RR Film 0.8 1.8 287 NA NA MD RR Film 0.6 1.6 695 NA NA BaseFilm 0.9 2.7 639 NA NA Thicker Base 1.52 4.4 682 NA NA Film

The results from Table I show that even with very low adhesive coating,superior Dynatup, MD tear resistance, and TD tear resistance propertiesare achieved compared to two layers of non-laminated film or one layerof thicker film. In particular, the results from Table I show adhesivelylaminating an MD RR film and a TD RR film can balance the MD and TD tearresistance. Furthermore, the individual values for the Dynatup, MD tearresistance, and TD tear resistance properties are unexpectedly higherthan the sum of the individual layers. Thus, the incrementally-stretchedadhesively-laminated films provide a synergistic effect.

More specifically, as shown by the results from Table I, the TD tearresistance of the incrementally-stretched adhesively-laminated films canbe greater than a sum of the TD tear resistance of the individuallayers. Similarly, the MD tear resistance of the incrementally-stretchedadhesively-laminated films can be greater than a sum of the MD tearresistance of the individual layers. Along related lines, the Dynatuppeak load of the incrementally-stretched adhesively-laminated films canbe greater than a sum of a Dynatup peak load of the individual layers.

Additionally, the results from Example 1 show that the coat weight ofadhesive applied to laminate the layers can range from light coatweights to heavy coat weights. In the case of light coat weights (e.g.,samples 3 and 4), that upon applying a strain to theincrementally-stretched adhesively-laminated film the first and secondfilm layers will delaminate prior to either the first or second filmlayers failing. This is indicated by the tensile peel numbers.Furthermore, once the layers delaminate under stress, they can reactindependently. Thus, Tables II and III indicate that the lightly adheredincrementally-stretched adhesively-laminated films have two tensile peakloads separated by considerable elongation.

Example 2

In Example 2, the same base layer of film as Example 1 was both MD andTD ring rolled using the same ring rolls as Example 1. The two MD and TDRR films were then laminated together using a butene-1-copolymer, hotmelt adhesive, Rextac® RT 2730 at five different coat weights shown inTables IV, V, and VI as samples 5-9.

TABLE IV Properties of Incrementally-Stretched Adhesively-LaminatedFilms (both layers MD and TD RR) Cali- Dynatup Coat Gage per Ten-Dynatup Energy Wt. by 1″ sile Peak to max Dart g/sq. Wt. Foot Peel Loadload (in. Drop ft. (mils) (mils) (g-f) (lb-f) lb-f) F50 (g) Sample0.0300 0.64 1.71 81.5 11.5 11.28 254.0 5 Sample 0.0150 0.65 1.85 25.510.3 9.61 6 Sample 0.0100 0.67 1.81 27.6 10.6 9.34 264.0 7 Sample 0.00750.66 1.79 2.27 9.7 10.99 8 Sample 0.0060 0.66 1.87 7.79 9.9 12.21 260.09 Comparison Data Thicker NA 0.9 0.88 NA 4.3 3.8 180 Base Film

TABLE V Properties of Incrementally-Stretched Adhesively-Laminated Films(both layers MD and TD RR) MD MD MD MD MD MD TD Tensile Tensile TensileTensile Tensile Tear Tear Yeild Peak 1 Strain 1 Peak 2 Strain 2 (g) (g)(lb-f) (lb-f) (%) (lb-f) (%) Sample 5 418 511 0.216 5.3 111.525 4.72120.474 Sample 6 349 441 0.224 5.2 128.574 5.62 146.256 Sample 7 353 4060.204 5.5 138.238 4.62 113.35 Sample 8 335 423 0.185 6.0 157.542 5.68143.349 Sample 9 319 450 0.194 5.8 145.162 4.79 140.156 Comparison DataThicker 262 843 1.42 7.2 466 NA NA Base Film

TABLE VI Properties of Incrementally-Stretched Adhesively- LaminatedFilms (both layers MD and TD RR) TD TD TD TD TD Tensile Tensile TensileTensile Tensile Yeild Peak 1 Strain 1 Peak 2 Strain 2 (lb-f) (lb-f) (%)(lb-f) (%) Sample 5 0.867 2.1 497.5 2.52 549.26 Sample 6 0.853 2.0 4842.09 494.31 Sample 7 0.932 2.6 525.7 2.50 532.15 Sample 8 0.849 2.4553.7 2.39 566 Sample 9 0.814 2.1 599.6 2.10 656.98 Comparison DataThicker Base 1.52 4.4 682 NA NA Film

The results from Tables IV, V, and VI show that even with very lowadhesive coating, superior Dynatup, MD tear resistance, and TD tearresistance properties are achieved compared to two layers ofnon-laminated film or one layer of thicker film. Additionally, theresults from Tables IV, V, and VI in conjunction with the ComparisonData from Tables I, II, and III show that incrementally-stretchedadhesively-laminated films of one or more implementations can allow fora reduction in basis weight (gauge by weight) as much as 50% and stillprovide enhanced strength parameters.

In addition to allowing for films with less raw material yet enhancedstrength parameters, the results from Tables IV, V, and VI further showthat incrementally-stretched adhesively-laminated films of one or moreimplementations can have an increased gauge (i.e., caliper) despite thereduction in basis weight. Some consumers may associate thinner filmswith decreased strength. Indeed, such consumers may feel that they arereceiving less value for their money when purchasing thermoplastic filmproducts with smaller gauges. One will appreciate in light of thedisclosure herein that despite a reduction in raw material,incrementally-stretched adhesively-laminated films of one or moreimplementations may be and look thicker than a single layer of film witha higher basis weight. Thus, one or more implementations can enhance thelook and feel of a film in addition to enhancing the strength parametersof the film.

Example 3

In Example 3, one white layer of HDPE with a low MD tear resistance wascold stretched by MD ring rolling at 0.110 DOE. Another black layer ofLLDPE was cold stretched by MD ring rolling at 0.110 DOE followed by TDring rolling at 0.032 DOE and then laminated together with the sameadhesive. Again, with the two ply laminates superior properties wereobtained even at very low adhesive levels compared to a single ply filmas shown by the results of Tables VII-IX.

TABLE VII Dynatup and Tear Resistance of Incrementally-StretchedAdhesively- Laminated Films (1 layer MD RR and 1 layer MD and TD RR)Dynatup Coat Gage Dynatup Energy Dart Wt. by Peak to max Drop MD TDg/sq. Wt. Load load (in. F50 Tear Tear ft. (mils) (lb-f) lb-f) (g) (g)(g) Sample 10 0.0300 0.67 11.83 11.86 284 357 575 Sample 11 0.0150 0.6711.79 14.21 357 532 Sample 12 0.0100 0.67 10.99 10.77 288 373 502 Sample13 0.0075 0.67 11.80 11.60 360 530 Sample 14 0.0060 0.67 12.60 10.57 260385 535 Comparison Data Thicker NA 0.9 4.3 3.8 180 262 843 Base Film

TABLE VIII MD Tensile Properties of Incrementally-Stretched Adhesively-Laminated Films (1 layer MD RR and 1 layer MD and TD RR) MD MD MD MD MDTensile Tensile Tensile Tensile Tensile Yeild Peak 1 Strain 1 Peak 2Strain 2 (lb-f) (lb-f) (%) (lb-f) (%) Sample 10 0.304 5.1 135 2.25 325Sample 11 0.307 5.1 128 3.1 350 Sample 12 0.292 5.23 138 3.1 375 Sample13 0.265 3.75 161 2.25 375 Sample 14 0.332 5.25 119 2.75 350 ComparisonData Thicker Base 1.42 7.2 466 NA NA Film

TABLE IX TD Tensile Properties of Incrementally-Stretched Adhesively-Laminated Films (1 layer MD RR and 1 layer MD and TD RR) TD TD TD TD TDTensile Tensile Tensile Tensile Tensile Yeild Peak 1 Strain 1 Peak 2Strain 2 (lb-f) (lb-f) (%) (lb-f) (%) Sample 10 1.1 2.4 511 1.8 650Sample 11 1.1 1.9 506 1.25 600 Sample 12 1.1 2.2 516 1.8 650 Sample 131.1 1.9 470 1.7 560 Sample 14 1.1 2.2 482 1.25 600 Comparison DataThicker Base 1.52 4.4 682 NA NA Film

Example 4

In a fourth example, a bag formed from an incrementally-stretchedadhesively-laminated film were compared to single ply bags of heavierbasis weight using a consumer test with 17 lbs. of mixed garbage on anend use scale of 1-5. The laminate of two layers which wereindependently MD ring rolled and then TD ring rolled followed byadhesive lamination has an excellent score comparable to single layerbags of higher basis weight.

TABLE VIII End Use Testing Sample Gage by Wt. (mils) End use scoreIncrementally-Stretched 0.66 4.16 Adhesively-Laminated MD ring rolledsingle layer 0.80 4.08 Strainable network single layer 0.85 4.50

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

We claim:
 1. A method for forming an incrementally-stretchedadhesively-laminated film, comprising: providing a first film layercomprising a thermoplastic material; providing at least a second filmlayer; cold stretching one or more of the first film layer and thesecond film layer incrementally; and adhesively laminating the firstfilm layer to the second film layer.
 2. The method as recited in claim1, further comprising applying a coat weight of adhesive to one or moreof the first and second film layers such that upon applying a strain tothe incrementally-stretched adhesively-laminated film the first andsecond film layers will delaminate prior to either the first or secondfilm layers failing.
 3. The method as recited in claim 1, wherein theincrementally-stretched adhesively-laminated film has a basis weightless than a combined basis weight of the first and second films prior tocold stretching one or more of the first film layer and the second filmlayer.
 4. The method as recited in claim 2, wherein a MD tear resistanceof the incrementally-stretched adhesively-laminated film is greater thana sum of an MD tear resistance of the first film layer and an MD tearresistance of the second film layer.